Copper base alloys containing manganese and aluminium



United States Patent 88,920 4 Claims. c1. 75-4575 :This invention relates to copper base alloys containing manganese and aluminium, and to shaped articles, manufactured from such alloys.

It is known to have an alloy consist of 1 to 5% iron,

1 to 6% nickel, 6 to 9% aluminium, 10 to manganese and as balance substantially copper. Moreover, a monophase forging alloy is known, containing less than 5% iron, less than 6% nickel, between 5 and manga nese, 1 to 7-%- aluminium and 0.01 to 0.2% arsenic, antimony or phosphorus,- balance copper. The arsenic, antimony or phosphorus increase the corrosion resistance by preventing the aluminium from being extracted from the alloy. Such known alloy-s particularly have a composition of between 5 and 13% of manganese and experiments have been made with an alloy of 12% manganese.

Moreover, an alloy is known having 8.5% to 10% manganese, 8.5 to 10.5% aluminium, 2.5 to 5% iron, 2 to 3% nickel, less than 0.25% impurities such as zinc, lead and silicon, and the balance copper. Such alloys have a good resistance against corrosion and cavitation-erosioncorrosion in seawater.

This invention is based upon the discovery that the corrosion resistance and particularly the resistance against cavitation-erosion-corrosion of such .alloys in seawater, particularlyat high. relative water speeds, may be improved at such known manganese contents (about 10 to 16%) while maintaining good mechanical characteristics such as tensile strength, 0.2-yield limit, total elongation, contraction at rupture and fatigue strength under rotated bending both in air and in seawater, without increase of melting point, and while maintaining a good weldability, deformability in hot condition and extrudability if such an alloy is manufactured with the following composition:

Percent Iron 1 to 9 Nickel, if desired entirely or in part replaced by cobalt 0 to 7 Aluminium 3 to 9 Nickel and iron together; 3 to 14 Manganese 10 to 16 Zinc 1 to 7 Balance copper and usual impurities.

It has'moreover appeared in this respect that zinc is able to replace part of the aluminium in its influence on the mechanical characteristics and on the precipitation of the iron-rich phase during solidification of the molten alloy, whch influences the corrosion resistance. This means that during the manufacture of the molten bath of the alloy not'only aluminium (and if desired manganese) but also zinc may be used to correct the conditions and'the coin-position and finally the characteristics of the alloy. This facilitates manufacture. The influence of aluminium is so pronounced that the aluminium percentage is highly critical and small, possibly unintentional deviations of the aluminium content have a high influence. Zinc is less critical in this respect.

It has appeared that zinc has a so-called aluminium equivalent of about 0.3 to 0.4. It appears therefrom that 3,297,437 Patented Jan. 10, 1967 ice much more zinc could be added without great changes in characteristics than aluminium would entrain.

Zinc has a much lower melting point than manganese, which has lower aluminium equivalent than zinc, namely about 0.1 to 0.2. Thus less zinc than manganese is necessary for the same effect and zinc is not only more economical than manganese, but due to the low melting point of zinc it is possible to produce the melt more rapidly and with less heating energy, particularly with respect to final corrections of the bath.

The surprising character of the present invention appears from the fact that up tonow in comparable alloys with relatively high managanese content no zinc was used at all, such as in the alloy given above with 1 to 5% iron, 1 to 6% nickel, 6 to 9% aluminium, 10 to 15% manganese, balance copper. In the publication of the British Standards Institution: B.$ 1400: 1961: Schedule of Copper Alloy Ingots and Copper Alloy Castings, pages 65-68 for manganese-aluminium-copper alloys, to total absence of zinc is taken as a basis.

The invention will now further be explained on the basis of the following examples:

Example 1.The following elements were melted together in a suitable furnace:

Percent Iron 6.6

Nickel 2.7 Aluminium c 6.7 Manganese 11.7 Zinc 1.8

Balance copper and usual impurities.

The alloy was cast in a sand mold bonded by cement. Examination of a sample of this alloy gave the following values:

Tensile strength 95,000 p.s.i. Elongation at rupture 30% (1/d=5). Contraction at rupture 34.4%

Example II.In a suitable furnace an alloy was made which obtained the following composition:

Example III.-An alloy was made with the following composition:

Percent Iron 3 .2

Nickel 2.7

Aluminium 8.1

Manganese 11.9 Zinc 3 .6

Balance copper and usual impurities.

A sample was tested and gave the following results:

Tensile strength 115,000 p.s.i. Elongation at rupture 19.5% (1/d=5). Contraction at rupture 17%.

3 Example I V.-An alloy was made'with the following composition:

Example V.-An alloy was made with the following composition;

Percent Iron 6.6 Nickel 5.0 Aluminium 5.8 Manganese 15.4 Zinc 4.3 Balance copper and usual impurities.

A sample gave:

Tensile strength 103,000 p.s.i. Elongation at rupture 16% (1/d=5).

Contraction at rupture 15.4%.

Example VI.An alloy was made with the following composition:

Percent Iron 6.5 Nickel 2.7 Aluminium 6.5 Manganese 11.5 Zinc 4.1

Balance copper and usual impurities.

Testing of a sample gave the following results:

Tensile strength 97,000 p.s.i. 0.2 yield limit 42,000 p.s.i. Elongation at rupture 25% (1/d=5).

This alloy was with respect to its corrosion resistance and cavitation-erosion-corrosion resistance in seawater at a speed of 125 feet per second compared with the following known manganese-aluminium-cooper alloy: iron 2.74%, nickel 2.03%, aluminium 8.45%, manganese 12.04%, balance copper and impurities.

Aluminium equivalent 10.25.

Tensile strength 97,500 p.s.i.

0.2 yield limit 44,000 p.s.i. Elongation at rupture 18.3% (1/d=5).

It appeared from the comparison that the corrosion resistance of the alloy according to the invention, Example VI, was about 60% higher than of said known alloy. The cavitation-erosiou-corrosion resistance was about 100% better than of said known alloy.

Example VII.An alloy was made with the following composition:

Testing of a sample gave:

Tensile strength 72.6 kg./rnm. 0.2 yield limit 31.7 kg./mm. Elongation at rupture 22.9% (l/d=5).

The alloy was tested as indicated under Example VI and compared with the known alloy given in saidexample. The corrosion-resistance of the alloy accordingto the invention was about 15% better than of said known alloy. The cavitationerosion-corrosion resistance was also in this case about better than of said known alloy.

The alloy of Example VII was extruded and a sample of said extruded alloy had a tensile strength of 92,500 p.s.i., a 0.2 yield limit of 60,000 p.s.i. and an elongation at rupture of 32% (1/d=5).

Example VIIl.An alloy was made with the following composition:

Percent Iron 4.5 Nickel 2.1 Cobalt 0.8 Aluminium 6.4 Manganese 12.1 Zinc 4.9 Balance copper and impurities.

Testing of a sample thereof gave:

Tensile strength 102,000 p.s.i. Elongation at rupture 26.5% (1/d=5).

All percentages of alloy components given in this specification and in the attached claims relate to percentages by weight.

What we claim is:

1. An alloy having the following weight composition: 1 to 9% iron, up to 7% of a member selected from the class consisting of nickel, cobalt, and mixtures thereof, 3 to 9% aluminum, 10 to 16% manganese, 1 to 7% zinc, balance essentially copper, the sum of the iron and any nickel being 3 to 14%, in which the aluminum equivalent, calculated by adding to the aluminum percentage 0.15 times the manganese percentage and 0.35 times the zinc percentage, is between 7 and 13.

2. An alloy as claimed in claim 1, in which the aluminum equivalent is between 9 and 11.5.

3. An alloy having the following weight composition: 2 to 7% iron, 1 to 5% of a member selected from the class consisting of nickel, cobalt, and mixtures thereof, 5 to 8% aluminum, 10 to 16% manganese, 1.6 to 5.5% zinc, balance essentially copper, in which the aluminum equivalent, calculated by adding to the aluminum percentage 0.15 times the manganese percentage and 0.35 times the zinc percentage, is between 7 and 13.

4. An alloy as claimed in claim 3, in which the aluminum equivalent is between 9 and 11.5.

References Cited by the Examiner UNITED STATES PATENTS 2,085,416 6/1937 Corson 75157.5 2,372,152 3/1945 Whittaker et al. 75--157.5 3,134,669 5/1964 Putter et al 75161 FOREIGN PATENTS 880,325 12/1942 France. 762,235 11/1956 Great Britain. 868,276 5/ 1961 Great Britain.

DAVID L. RECK, Primary Examiner.

C. N. LOVELL, Assistant Examiner. 

1. AN ALLOY HAVING THE FOLLOWING WEIGHT COMPOSITION: 1 TO 9% IRON, UP TO 7% OF A MEMBER SELECTED FROM THE CLASS CONSITING OF NICKEL, COBALT, AND MIXTURES THEREOF, 3 TO 9, ALUMINUM, 10 TO 16% MANGANESE, 1 TO 7% ZINC, BALANCE ESSENTIALLY COPPER, THE SUM OF THE IRON AND ANY NICKEL BEING 3 TO 14%, IN WHICH THE ALUMINUM EQUIVALENT, CALCULATED BY ADDING TO THE ALUMINUM PERCENTAGE 0.15 TIMES THE MANGANESE PERCENTAGE AND 0.35 TIMES THE ZINC PERCENTAGE, IS BETWEEN 7 AND
 13. 